Enhanced Oil Recovery (EOR) may be used to increase oil recovery in fields worldwide. There are three main types of EOR, thermal, chemical/polymer and gas injection, which may be used to increase oil recovery from a reservoir, beyond what can be achieved by conventional means—possibly extending the life of a field and boosting the oil recovery factor.
Thermal enhanced recovery works by adding heat to the reservoir. The most widely practiced form is a steam-drive, which reduces oil viscosity so that it can flow to the producing wells. Chemical flooding increases recovery by reducing the capillary forces that trap residual oil. Polymer flooding improves the sweep efficiency of injected water. Miscible gas injection works in a similar way to chemical flooding. By injecting a fluid that is miscible with the oil, trapped residual oil can be recovered.
Oil is often withdrawn from a reservoir in a non-uniform manner. That is, most of the oil is produced from the more easily drainable sections of the formation, and relatively little oil comes from the less easily drainable sections. This is especially true in highly fractured reservoirs or those having sections of widely varying permeability wherein oil is left in the less accessible portions of the reservoir. In such reservoirs an ordinary secondary recovery flooding treatment is often of limited value, as the injected fluid tends to sweep or pass through the same sections of the formation which are susceptible to good drainage, thus either bypassing or entering to only a limited extent those sections of the formation which cannot be readily drained.
Referring to FIG. 1, there is illustrated prior art system 100. System 100 includes underground formation 102, underground formation 104, underground formation 106, and underground formation 108. Production facility 110 is provided at the surface. Well 112 traverses formations 102 and 104, and terminates in formation 106. The portion of formation 106 is shown at 114. Oil and gas are produced from formation 106 through well 112, to production facility 110. Gas and liquid are separated from each other, gas is stored in gas storage 116 and liquid is stored in liquid storage 118. Gas in gas storage 116 may contain hydrogen sulfide, which must be processed, transported, disposed of, or stored.
U.S. Pat. No. 6,241,019 discloses extracting a liquid (such as oil) from a porous medium, where the liquid is subjected to pulses that propagate through the liquid flowing through the pores of the medium. The pulses cause momentary surges in the velocity of the liquid, which keeps the pores open. The pulses can be generated in the production well, or in a separate excitation well. If the pulses travel with the liquid, the velocity of travel of the liquid through the pores can be increased. The solid matrix is kept stationary, and the pulses move through the liquid. The pulses in the liquid can be generated directly in the liquid, or indirectly in the liquid via a localised area of the solid matrix. U.S. Pat. No. 6,241,019 is herein incorporated by reference in its entirety.
Co-pending U.S. Patent Application Publication No. 2006/0254769, published Nov. 16, 2006, discloses a system including a mechanism for recovering oil and/or gas from an underground formation, the oil and/or gas comprising one or more sulfur compounds; a mechanism for converting at least a portion of the sulfur compounds from the recovered oil and/or gas into a carbon disulfide formulation; and a mechanism for releasing at least a portion of the carbon disulfide formulation into a formation. U.S. Patent Application Publication No. 2006/0254769 is herein incorporated by reference in its entirety.
There is a need in the art for improved systems and methods for enhanced oil recovery. There is a need in the art for improved systems and methods for enhanced oil recovery with pressure pulsing. There is a need in the art for improved systems and methods for enhanced oil recovery with reduced fingering and/or with a more uniform front.